Lancaster scientists have played a key role in solving a neutrino mystery that has challenged researchers for decades.
An international team, including researchers from Lancaster University, worked on the MicroBooNE experiment at the US Department of Energy's Fermi National Accelerator Laboratory near Chicago.
MicroBooNE, a state-of-the-art detector filled with liquid argon, studied neutrinos coming from two separate particle beams at Fermilab over a period of six years.
The experiment brought together nearly 200 researchers from 40 institutions across six countries.
Funded by the Science and Technology Facilities Council (STFC), scientists from Lancaster, Cambridge, Edinburgh, Imperial College London, Manchester, Oxford, Queen Mary University of London and Warwick played a central role in this international programme.
The new results, published in Nature, found no evidence of a long-suspected fourth type of neutrino, known as the 'sterile neutrino' with 95% certainty.
Ruling out this long-suspected particle sharpens the search for physics beyond the Standard Model, bringing scientists a step closer to uncovering the true nature of neutrinos and the fundamental laws that govern the universe.
Lancaster scientists supported the development and final results of the analysis via various roles in the MicroBooNE collaboration.
Physics Professor Jaroslaw Nowak is a senior convener of the group working to understand neutrino interactions.
Professor Nowak said: "The previous experiment I worked on, MiniBooNE, showed the existence of phenomena in neutrino physics we don't understand. The new result shows that the simplest, yet groundbreaking, explanation cannot solve this almost 20-year-old mystery. The next step will be to use the short-baseline program at Fermilab, using data from three detectors, to validate other hypotheses."
Lancaster's Dr Andrew Blake was part of the team that created software that enabled many of the results from the experiment and built confidence that the recent results are validated.
Dr Isobel Mawby, also from Lancaster, is a convener of the reconstruction software group working on optimising algorithms to increase precision in MicroBooNE experiment results.
Dr Mawby said: "MicroBooNE has unprecedentedly combined data from the NuMI and BNB neutrino beams to conclusively rule that sterile neutrinos - a hypothetical type of neutrino - are not the source of the low-energy excess seen by LSND and MiniBooNE. I think this is an exciting time for our field, as we now turn to SBND and ICARUS in the hope that we will uncover new physics to explain the origin of this long-standing anomaly."
Lancaster PhD students, Ishanee Pophale and Niam Patel, worked on the validation of the new data used in this analysis and studies on how the MicroBooNE detector's sensitivity to ionisation electrons changes in periods of low liquid argon purity, both of which are essential to the results. Former Lancaster MSc by Research student, Tusharadri Mahmud, supported the effort by running a data processing campaign.
With sterile neutrinos now ruled out, the mystery of neutrinos remains. MicroBooNE is continuing the search for new physics and delivering vital data on how neutrinos behave in liquid argon, crucial knowledge for future experiments, including DUNE.
